Exhaust Gas Recirculation System

The Exhaust Gas Recirculation (EGR) system reduces oxides of Nitrogen (NOx) in the engine exhaust and helps prevent detonation (engine knock). Under normal operating conditions, engine cylinder temperature can reach over 3000°F (1649°C). The formation of NOx increases proportionally with combustion temperature. To reduce the emission of these oxides, cylinder temperature must be lowered. The system allows a predetermined amount of hot exhaust gas to recirculate and dilute the incoming air/fuel mixture. The diluted mixture lowers temperatures during combustion. The EGR system consists of the following components:

EGR tube

EGR valve

Electric EGR Transducer (EET)

Connecting hoses

The electric EGR transducer container an electrically operated solenoid and a backpressure transducer. The Powertrain Control Module (PCM) operated the solenoid, determining when to energize the solenoid. Exhaust system backpressure controls the transducer.

When the PCM energizes the solenoid, vacuum doesn't reach the transducer. Vacuum flows to the transducer when the PCM de-energizes the solenoid. When exhaust system backpressure becomes high enough, it fully closes a bleed valve in the transducer. When the PCM de-energizes the solenoid and backpressure closes the transducer bleed valve, vacuum flows through the transducer to operate the EGR valve.

De-engergizing the solenoid, but not fully closing the transducer bleed hole (because of low backpressure), varies the strength of vacuum applied to the EGR valve. Varying the strength of the vacuum changes the amount of EGR supplied to the engine. This provides the correct amount of exhaust gas recirculation for different operating conditions. This system does not allow EGR at idle.

COMPONENT TESTING

EGR System On-Board Diagnostics

The PCM performs an on-board diagnostic check of the EGR system. The diagnostic system uses the electric EGR transducer for the system tests.

The check activates only during certain conditions. When the conditions are met, the PCM energizes the transducer solenoid to disable the EGR system. The PCM checks for a change in the heated oxygen sensor signal. If the air/fuel ratio goes lean, the PCM will try to enrich the mixture. The PCM records a Diagnostic Trouble Code (DTC) if the EGR system is not operating properly. After registering a DTC, the PCM turns on the Check Engine lamp (malfunction indicator) after 2 consecutive trips. There are 2 types of failures sensed by the PCM; a short or open in the circuit, or a mechanical failure or loss of vacuum. The Malfunction Indicator Lamp (MIL) denotes the need for service.

If you find a problem indicated by the MIL and a DTC is set, first check for proper operation of the EGR system. If the system tests properly, check the system using Chrysler's DRB® or equivalent scan tool. Make sure to follow all of the instructions included with the scan tool.

EGR System Test

CAUTION

ALWAYS block the drive wheels and apply the parking brake anytime you are performing a test or adjustment in which the engine must be running.

1995-96 VEHICLES

See Figure 1

A failed or malfunctioning EGR system can cause engine spark knock, hesitation or sags, rough idle, stalling and/or increased emissions. To make sure the EGR system is operating properly, all passages and moving parts must be clean of deposits that could cause plugging or sticking. Make sure the hoses don't leak and replace any components that do leak.

Check the hose connections between the intake manifold, EGR solenoid and transducer, and the EGR valve. Replace any hardened, cracked, melted or leaking hoses. Repair or replace faulty connectors.

Check the EGR control system and EGR valve with the engine fully warmed up and running with the engine coolant temperature at 170°F (77°C) or over. With the transmission in Neutral and the throttle closed, allow the engine to idle for about 70 seconds.

Abruptly accelerate the engine to about 2,000 rpm, but NOT over 3,000 rpm. The EGR valve stem should move when accelerating the engine.

Repeat the test a few times to confirm movement. If the valve stem moves, the EGR system is operating properly. If the stem doesn't move, then the EGR system is not operating properly.

With the engine running at idle speed, slowly apply vacuum. Engine speed should begin to drop when the applied vacuum reaches 2.0-3.5 in. Hg. Engine speed may drop quickly or the engine may even stall. This indicates that EGR gas is flowing through the system.

If the engine speed doesn't drop when applying the vacuum, remove both the EGR valve and EGR tube, and check for plugged passages; clean or replace as necessary.

1997-98 VEHICLES

Check the condition of all EGR system hoses and tubes for leaks, blockage, cracks, kinks or hardening. Repair or replace them as necessary before beginning the test.

Make sure the hoses at both the EGR valve and EGR valve control are connected properly, and that the electrical connector is firmly attached at the valve control.

To check EGR system operation, connect a DRB® or equivalent scan tool to the 16-way data link connector. (The data link connector is located on the lower edge of the instrument panel, near the steering column.) Make sure to follow all of the manufacturer's instructions when connecting the scan tool and testing the EGR system.

After checking the system with the scan tool, proceed to the remaining EGR valve control tests.

EGR Gas Flow Test

See Figures 1 and 2

Use this test to see if exhaust gas is flowing through the EGR system.

The engine must be started, running and at normal operating temperature for this test. This test is not to be used as a complete test of the EGR system, but in conjunction with the other system tests.

All engines are equipped with 2 fittings on the EGR valve, as shown in the accompanying figure. The upper fitting (located on the vacuum motor) supplies engine vacuum to a diaphragm within the EGR valve for valve operation. The lower fitting (located on the base of the EGR valve) is used to supply exhaust backpressure to the EGR valve control.

Disconnect the rubber hose from the vacuum motor fitting on top of the EGR valve vacuum motor.

Start the engine. Use a hand-held vacuum gauge to apply about 5 in. (17 kPa) of vacuum to the fitting on the EGR valve motor.

While applying a minimum 3 in. (10 kPa) of vacuum, and with the engine running at idle speed, the idle speed should drop or the engine may even stall, if the vacuum is applied quickly. This indicates that exhaust gas is flowing through the EGR tube between the intake and exhaust manifolds.

If the engine speed did not change, the EGR valve may be defective or the EGR tube may be plugged with carbon, or the passages in the intake and/or exhaust manifold may be plugged with carbon. Perform the following to see if the components are plugged:

Remove the EGR valve from the engine, as outlined later in this section.

Apply vacuum to the vacuum motor fitting and check the stem on the valve. If it's moving, the EGR valve is working properly and the problem is either a plugged EGR tube or plugged passages at the intake or exhaust manifolds (refer to the next step).

Remove the EGR tube between the intake and exhaust manifolds. Check and clean the EGR tube and its related openings on the manifolds.

Do not try to clean the EGR valve. If the valve shows evidence of heavy carbon build-up near the base, replace it.

EGR Valve Leakage Test

See Figures 1 and 2

If the engine will not idle, stalls while idling or the idle is rough or slow, the poppet valve, located at the base of the EGR valve, may be leaking in the closed position.

The engine should be
OFF
for the following test.

Disconnect the rubber hose from the fitting at the top (vacuum motor) side of the EGR valve, and perform the following:

Connect a hand-held vacuum pump to this fitting.

Apply 15 in. (51 kPa) of vacuum to the pump, then observe the gauge reading on the pump.

If the vacuum falls off, the diaphragm in the EGR valve has ruptured.

Replace the EGR valve, as outlined later in this section.

Go on to the next step.

The EGR valve, valve control and attaching hoses are replaced as an assembly.

A small metal fitting (backpressure fitting) is located at the base of the EGR valve. A rubber backpressure hose connects it to the backpressure fitting on the EGR valve control. Disconnect this hose from the EGR valve fitting.

Remove the air cleaner inlet tube from the throttle body.

Using compressed air from an air nozzle with a rubber tip, apply about 50 psi (345 kPa) of regulated air to the metal backpressure fitting on the EGR valve.

By hand, open the throttle to the wide open position. Air should NOT be heard coming from the intake manifold while applying air pressure to the fitting.

If air CAN be heard coming from the intake manifold, the poppet valve is leaking at the bottom of the EGR valve. Replace the EGR valve.

Electric EGR Transducer Solenoid Test

See Figures 3 and 4

Before disconnecting any vacuum hoses, place an identification mark on each of them for correct installation.

Label, then disconnect each vacuum hose from the electric EGR transducer solenoid.

Using 2 jumper wires, connect one between the transducer solenoid terminal and positive battery terminal, and the second wire to the remaining solenoid terminal.

Connect and disconnect the second jumper wire to the negative battery terminal side, while applying vacuum and positive pressure to check airtightness. With vacuum applied, this test should produce the following results:

Jumper wire disconnected and positive pressure not applied should produce a vacuum leak.

Using an ohmmeter, measure resistance between the transducer solenoid terminals.

On 2.0L and 2.4L engines, the ohmmeter should read 25-35 ohms at approximately 68°F (20°C). On 2.5L engines, the ohmmeter should read 31-41 ohms at approximately 68°F (20°C).

If the resistance measures out of specifications, replace the electric EGR transducer solenoid.

REMOVAL & INSTALLATION

EGR Valve and Electric Transducer

See Figures 2 and 5 through 12

Although the EGR valve and Electric EGR Transducer (EET) can be removed separately, they must be replaced as a pair, since they are calibrated together.

On the 2.0L and 2.4L engines, the EGR valve and EET attach to the rear of the cylinder head. On 2.5L engines, the EGR valve is attached to the rear of the front cylinder head, and the EET is attached to the front exhaust manifold.

Fig. Fig. 9: Removing the TCM from the vehicle will allow better access to the EGR valve

If necessary on the 2.5L engine, loosen the 60-way connector retaining screw and detach the connector from the Transmission Control Module (TCM), then unscrew the mounting fasteners and remove the TCM from the engine compartment.